public IReadOnlyList<Domain> GetDomains()

{
  await QueuedTask.Run(() =>
  {
    using (var kg = GetKnowledgeGraph(url))
    {
      //Get all the domains in the KG
      var domains = kg.GetDomains();
      var sb = new SchemaBuilder(kg);

      foreach (var domain in domains)
      {
        //skip the special provenance domain
        var name = domain.GetName();
        if (string.Compare(name, "esri__provenanceSourceType", true) == 0)
          continue;//skip this one

        //Delete all other domains
        if (domain is ArcGIS.Core.Data.RangeDomain rd)
          sb.Delete(new RangeDomainDescription(rd));
        else if (domain is ArcGIS.Core.Data.CodedValueDomain cvd)
          sb.Delete(new CodedValueDomainDescription(cvd));
      }

      try
      {
        //note: will throw an InvalidOperationException if there are no operations
        //to run. Will also delete associated fields dependent on deleted domain(s)
        if (!kg.ApplySchemaEdits(sb))
        {
          var err_msg = string.Join(",", sb.ErrorMessages.ToArray());
          System.Diagnostics.Debug.WriteLine($"Delete domains error: {err_msg}");
        }
      }
      catch (Exception ex)
      {
        System.Diagnostics.Debug.WriteLine(ex.ToString());
      }
    }
  });
}

KnowledgeGraph GetKnowledgeGraph(string url)
{
  var kg_props =
    new KnowledgeGraphConnectionProperties(new Uri(url));
  return new KnowledgeGraph(kg_props);
}